The invention relates to a multi-stage ejector pump. More particularly, the invention relates to a multi-stage ejector pump having at least one housing element with at least one pressure gas intake opening, at least one suction gas intake opening, at least one exhaust gas opening, and at least one nozzle arrangement. The nozzle arrangement includes at least two nozzles (e.g., pressure gas nozzle, diffuser) positioned coaxially behind one another inside the housing element and axially spaced at distances from one another. The housing element includes a nozzle-receiving shaft having an essentially continuous shaft wall and at least one wall opening, an ejector step for the suction gas intake in the suction gas intake slit and the nozzles that equipped with at least one circumference sealing arrangement.
For the simple manufacture of multi-stage ejector pumps, it is known in the art how to assemble the housing of the pump from individual parts, such as from a pump kit. Each part of the housing in the kit carries one of the nozzles in a transverse wall that intersects an interior space of the housing. If a multiple stage ejector pump is to be designed, this transverse wall of the housing may also carry several nozzles arranged side by side. Through the assembly of the parts of the housing, the pump is then ready for use. Here, installing the nozzles, e.g. by gluing them in or even by integrating the nozzle into the separating wall as a single part, is comparatively simple. However, many hermetic surfaces exist between the parts of the housing. The range of available designs for a compact pump arrangement are very limited. An ejector pump that is representative of the prior art for modular multi-stage pumps is disclosed in DE-C1-44 91 977, FIGS. 7 to 9.
There are also ejector pumps known, in which a continuous cast profile with inner separating walls is used, and the nozzles are installed in the individual separating walls angled to the axis of the profile through holes drilled in a terraced pattern. Most of the nozzles are located in the hollow spaces on both sides of the separating walls, which serve to distribute the gas. Although the above-mentioned hermetic surfaces are eliminated, adapting and tightening the nozzles is still difficult. Moreover, the compactness of such ejector pumps is not significantly better than the modular pumps mentioned above. For tight spaces, there are ejector pumps known with a compact design, in which the nozzles are pushed from different sides against a catch into a drilled hole in the housing to receive them. Due to such a design, ejector pumps of this kind can only be designed with one stage. It is not possible to interchange the nozzles.
Finally, there is a general multi-stage ejector that is known from DE 44 91 977, FIGS. 1 to 5, which is characterized in that a two-stage ejector nozzle system is designed as one piece and can be pushed into a nozzle-receiving shaft. In order to attain multi-stage properties, the one-piece axially designed nozzle body is connected with a suction opening by means of sections with a greater inside diameter. One of the limitations of using this type of pump design is that the manner of making the nozzles requires very costly shaping steps in the area of the undercut zones. Another limitation of this design is that only a cylindrical or conical course of the nozzle cross-sections located behind one another can be achieved. The supply of the pressure gas and the suction gas chamber are housed in flange-mounted components, which are connected with the housing body featuring the one-piece nozzle with screws, with the use of a large number of filigrane gaskets. The connection for the pressure gas and the connection for the suction gas are located in a lateral face arranged parallel to the nozzle channel inside the walls of the flange-mounted components of the housing. These gas connections face away from the nozzle axis at a right angle. The large number of additional sealing surfaces, in the area of the flange-mounted components of the housing makes this ejector pump prone to leaks. This risk is only slightly attenuated with the closed lateral walls of the housing base that run in a U shape along the nozzle configuration.
In view of the deficiencies of prior art ejector pumps, there is a need for a less costly ejector pump that has a compact design and is less prone to leakage during operation.
The principal problem to be solved by the present invention is to design a generic multi-stage ejector pump that is compactly constructed, includes interchangeable nozzles and has a high degree of effectiveness. To resolve the problems of prior art multi-stage pumps, there is provided a multi-stage ejector pump which includes at least one housing element. The housing element includes at least one pressure gas intake opening, at least one suction gas intake opening, at least one exhaust gas opening, and at least one nozzle arrangement. The nozzle arrangement, such as an ejector nozzle system, includes at least two nozzles (e.g., pressure gas nozzle and/or one or more diffusers) that are positioned coaxially behind one another inside the housing element and axially spaced at distances from one another. The ejector nozzles also includes an exhaust gas outlet opening, at least one pressure gas intake opening, and at least one suction gas intake slit between adjacent nozzles and an exhaust gas outlet opening. The housing element also includes a nozzle-receiving shaft (e.g., a drilled hole) having an essentially continuous shaft wall and at least one wall opening (e.g., connection opening). The housing element also includes a step for the suction gas intake in the suction gas intake slit. The nozzles on their outer circumference are equipped with at least one circumference sealing means. The ejector nozzle system is designed to be axially inserted into the nozzle-receiving shaft. The ejector nozzle system also includes a set of individual nozzle spacers. The nozzles are also equipped with support elements that are axially spaced for its tilt-free or low-tilt support in relation to the shaft wall when the nozzles are inserted into the nozzle-receiving shaft. At least one clamping means, such as a connection plate, is provided to axially clamp or hold in position the individual nozzles and the nozzle spacers in the nozzle-receiving shaft.
In one embodiment of the invention, the ejector nozzle system should consist of a set of individual nozzles (e.g., pressure gas nozzle, diffuser) and nozzle spacers, whereby the spacers leave open a space for the entry of gas between the adjacently spaced nozzles. As periodically referred to in this specification, the pressure gas nozzle and/or one or more diffusers of the ejector nozzle system are referred to as nozzles. The nozzles can be inserted into the nozzle-receiving shaft one after the another. By using this arrangement of nozzles, each of the nozzles can be shaped at both ends in a manner that will increase their performance. In addition, each individual nozzle has at least two support elements that are axially spaced to provide for a tilt-free or low-tilt support in relationship to the shaft wall. Only in this way is the design of individual nozzles with optimized performance possible, and which provides for the simple orienting of the nozzles to a common nozzle axis, without the need to glue the nozzles on to the nozzle-receiving shaft. While a press fit of the nozzle is conceivable, preferably O-rings are used as a means of sealing the outer circumference of each individual nozzle. The support elements can be cams that are distributed around the circumference of the nozzles, or something similar, but they can also be O-rings or similar means of sealing. The use of cams have the advantage of fulfilling a twofold function, since the cams serve as means of sealing at the same time as providing a tilt-free or low-tilt support. In order to position the nozzles and the nozzle spacers with precision, at least one means of clamping is provided. Thereby the nozzles with their nozzle spacers are axially clamped or held in position.
In another embodiment of the invention, the spacers can basically be provided on the housing element, for example in the form of steps in the nozzle-receiving shaft. However, according to the invention, because the spacers can be more simply manufactured and more easily adapted to the desired arrangement of nozzles, the spacers are preferably provided as separate or one piece one piece components. In addition, the spacers are preferably eccentrically positioned on the nozzles. The spacers, however designed, are inserted into the nozzle-receiving shaft. A particular high level of performance is attained when the spacers are equipped with slim catches or similar protrusions on one nozzle front end. It is preferable to provide only one single spacer of this kind. A preferred arrangement of the one or the several nose-shaped spacers is selected in such a way that, between two adjacent nozzles, the spacers are assigned to the nozzles in peripheral areas with low levels of flow, for example, on the side of the nozzles located opposite the gas entry side.
In another embodiment of the invention, the suction chambers are positioned parallel to the nozzle receiving shaft. The use of such a the suction chamber orientation allow for the suction chambers to be simply designed in a compact manner the housing. In accordance with this embodiment, there is preferably at least one drilled hole for gas suction. The drill hole is preferably designed as a drilled pocket hole. The drill hole includes O-rings on the outer circumference of the drill hole, and flap valves are provided to create a seal for the drill. The suction gas shaft is positioned parallel to the nozzle receiving shaft to reduce the number of sealing locations, while making the manufacture of the pump simpler and the arrangement of the gas feed and exhaust lines more compact.
In still another embodiment of the invention, the nozzle receiving shaft and the drilled hole for the suction gas both have a stepped change in diameter in the direction of the axis. This step change in diameter of the nozzle-receiving shaft and the drilled hole for the suction gas is advantageous in that the hermetically sealing O-rings can be inserted by sliding only along a short region of the shaft and near the final position of the O-rings along the wall of the shaft. In the area where the diameter of the steps is greater, contact with nozzles having smaller diameters can be eliminated.
In yet another embodiment of the invention, the compactness of the pump is further improved by providing a drilled hole for the suction gas that extends parallel to the nozzle-receiving shaft. The drilled hole for the suction gas provides a passageway to supply pressured gas to the pump. The axis of this drilled hole essentially and advantageously lies in parallel plane with the axis of the nozzle receiving shaft and the drilled hole for the suction gas. Using this design, the drill hole for the suction gas, the drill hole for the exhaust gas and the drill hole for the pressure gas are all parallel to the same longitudinal axis. As such, the suction gas, the exhaust gas and the pressure gas flow along parallel plane when entering or exiting the housing element of the multi-stage ejector pump. Due to this parallel planar arrangement of the drill hole for the suction gas, the drill hole for the exhaust gas and the drill hole for the pressure gas, a flat cubical block of light material or plastic can be developed as the housing element. This block of material of plastic may be created from drilling out of a solid blank or formed by an injection mold process. The parallel arrangement of the nozzle-receiving shaft with the suction gas shaft and/or the drilled hole for the pressure gas (pressure gas shaft) in a single housing block is of independent inventive significance.
In still yet another embodiment, prior art control valves can be used for the switching on and off of the vacuum function. In addition, control valves can also be used to control the drawing off of gas from the housing element. The prior art control valves are positioned in drilled holes that can run somewhat at a right angle through the drilled hole for the pressure gas and can extend into the nozzle receiving shaft. By this configuration for the control valves, a very short overall length of the ejector block is made possible. The control valves can be moved back and forth inside valve sleeves. The valve sleeves are set into the drilled holes for the control valves by means of O-rings and are clamped in their axis direction by a valve plate screwed on to the ejector block. The valve plate contains, in a manner that is known, electromagnetic pilot or servo valves, which create or interrupt a fluid connection between the pressure gas and the valve, thus pneumatically opening or closing the control valves.
In a further embodiment of the invention, the multi-stage ejector pump according to the invention can be used to produce a vacuum, for example for handling applications (conveying sheet metal press production lines for vehicle body parts, pick-and-place applications in plastic injection molding and the like). The multi-stage ejector pump is extremely compact and lightweight and can integrate functions in a simple manner (e.g., the electrical control of switching the vacuum on and off, the electrical control of switching the blowing off, and/or the monitoring of the level of the vacuum).
In comparison to known multi-stage compact ejectors, whose level of efficiency is, as a rule, between 0.4 and 0.7 parts suction air per part of applied pressure air, levels of efficiency of 1.2 to 2 parts suction air per part of applied pressure air can be attained with the invention. This is attained, on the one hand, because the multi stages, particularly two stages, of the ejector pump are simple to achieve, and, on the other hand, because of the possibility of shaping the valve cross-section to foster flow, despite the compact design. Because of the simpler construction of the ejector pumps according to the invention, vacuum pumps with varying performance levels can be made quickly and at low cost. Only the nozzle systems of the multi-stage pump of the present invention needs to be changed or be correspondingly set into the ejector block at hand. All parts are easily accessible and can be cleaned thoroughly, in the event performance diminished because dirt has been sucked in. Furthermore the fact that the ejector block can be separated from the nozzles and valves makes disassembly very simple, in the event it is taken off line.
In summary, the present invention pertains to an improved multistage ejector pump. The multi-stage ejector pump includes at least one housing element. The housing element includes at least one pressure gas intake opening, at least one suction gas intake opening, at least one exhaust gas opening, and at least one nozzle arrangement. The nozzle arrangement such as an ejector nozzle system, includes at least two nozzles (e.g., pressure gas nozzle and/or one or more diffusers) that are positioned coaxially behind one another inside the housing element and axially positioned from one another. The nozzle arrangement also includes an exhaust gas outlet opening, at least one pressure gas intake opening, and at least one suction gas intake slit between adjacent nozzles and an exhaust gas outlet opening. The housing element includes a nozzle-receiving shaft (e.g., a drilled hole) having an essentially continuous shaft wall and at least one wall opening (e.g., connection opening). The housing element also includes a stepped opening size for the suction gas intake in the suction gas intake slit. The nozzles on their outer circumference are equipped with at least one circumference sealing means, and the ejector nozzle system is axially insertable into the nozzle-receiving shaft. The ejector nozzle system also includes a set of nozzle spacers. The nozzles are equipped with support elements that are axially spaced to provide for tilt-free or low-tilt support in relation to the nozzle receiving-shaft and which support elements can be inserted into the nozzle-receiving shaft. At least one clamping means, such as a connection plate, is provided to axially clamp or hold in position the individual nozzles and the nozzle spacers in the nozzle receiving shaft.
In one additional aspect of the invention, the nozzle spacers, when the suction-gas intake slits between the nozzle front ends are released, are insertable between adjacent nozzles and can be inserted into the nozzle-receiving shaft.
In still another additional aspect of the invention, the spacers are shaped as slender noses or similar protrusions on one front end of a nozzle.
In yet another additional aspect of the invention, a single spacer is positioned in an area with low gas flow in the periphery area of the nozzles (e.g., eccentrically).
In still yet another additional aspect of the invention, a suction chamber is provided in a drilled hole for the suction gas and is positioned essentially parallel to the nozzle-receiving shaft.
In a further additional aspect of the invention, flap valves can be inserted into the drilled hole for the suction gas to form a hermetic seal.
In still a further additional aspect of the invention, the nozzle-receiving shaft and/or the drilled hole for the suction gas are made as drilled holes that are stepped or tiered in their diameter.
In still yet a further additional aspect of the invention, the nozzles and/or the flap valves can be inserted from a single side into a dead-end drilled hole (e.g., nozzle-receiving shaft and/or drilled hole for the suction gas).
In another additional aspect of the invention, a drilled hole for the pressure gas extends essentially parallel to the nozzle-receiving shaft.
In still another additional aspect of the invention, the housing element is shaped as a flat cubical block made of light material or plastic.
In yet another additional aspect of the invention, approximately at a right angle to the nozzle-receiving shaft, at least one drilled passage hole is provided to the drilled hole for the pressure gas and/or to the drilled hole for the suction gas.
In still yet another additional aspect of the invention, at least one control valve is placed in a drilled hole to receive a valve that connects the drilled hole for the pressure gas and the nozzle-receiving shaft and controls the flow of the pressure gas through the connection opening.
In a further additional aspect of the invention, a control valve includes a valve guide sleeve in the area of the drilled hole for the pressure gas.
In still a further additional aspect of the invention, the drilled hole for the pressure gas exhibits at least one bypass line between the inside of the drilled hole and the control valve that is controlled by a switch valve, in order to activate the control valve.
In yet a further additional aspect of the invention, the control valve exhibits a twofold effective tightening piston with differing piston surfaces on each of its sides.
The above mentioned components, as well as those claimed and those described in the embodiment, to be used according to the invention, are not subject to any special exception conditions, as to their size, shape, material selection and technical design, so that the selection criteria known in each particular area of application can find application in the claims, without exception.